Degree-constrained spanning tree: Difference between revisions

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In [[graph theory]], a '''degree-constrained spanning tree''' is a [[spanning tree (mathematics)|spanning tree]] where the maximum [[Degree (graph theory)|vertex degree]] is limited to a certain [[Constant (mathematics)|constant]] ''k''. The '''degree-constrained spanning tree problem''' is to determine whether a particular [[Graph (discrete mathematics)|graph]] has such a spanning tree for a particular ''k''.

==Formal definition==

Input: ''n''-node undirected graph G(V,E); positive [[integer]] ''k'' ≤< ''n''.

Question: Does G have a spanning tree in which no [[Node (computer science)|node]] has degree greater than ''k''?

==NP-completeness==

This problem is [[NP-complete]] {{harv|Garey|Johnson|1979}}. This can be shown by a [[Reduction (complexity)|reduction]] from the [[Hamiltonian path problem]]. It remains NP-complete even if ''k'' is fixed to a value ≥&nbsp;2. If the problem is defined as the degree must be ≤&nbsp;''k'', the ''k'' = 2 case of degree-confined spanning tree is the Hamiltonian path problem.

==Degree-constrained minimum spanning tree==

This problem is [[NP-complete]]. This can be shown by a reduction from the [[Hamiltonian path problem]]. It remains NP-complete even if ''k'' is fixed to a value ≥&nbsp;2. If the problem is defined as the degree must be ≤&nbsp;''k'', the ''k'' = 2 case of degree-confined spanning tree is the Hamiltonian path problem.

On a weighted graph, a Degree-constrained minimum spanning tree (DCMST) is a degree-constrained spanning tree in which the sum of its edges has the minimum possible sum. Finding a DCMST is an NP-Hard problem.<ref>Bui, T. N. and Zrncic, C. M. 2006. [http://www.cs.york.ac.uk/rts/docs/GECCO_2006/docs/p11.pdf An ant-based algorithm for finding degree-constrained minimum spanning tree.]

In GECCO ’06: Proceedings of the 8th annual conference on Genetic and evolutionary computation, pages 11–18, New York, NY, USA. ACM.</ref>

Heuristic algorithms that can solve the problem in polynomial time have been proposed, including Genetic and Ant-Based Algorithms.

==Approximation Algorithm==

{{harvtxt|Fürer and |Raghavachari|1994}} gavegive an approximationiterative polynomial time algorithm forwhich, thegiven problema whichgraph either<math>G</math>, showsreturns thata therespanning istree with maximum degree no treelarger ofthan <math>\Delta^* + 1</math>, where <math>\Delta^*</math> is the minimum possible maximum degree over all spanning trees. Thus, if <math>k or= returns\Delta^*</math>, such an algorithm will either return a spanning tree of maximum degree <math>k</math> or <math>k+1</math>.

==References==

{{Reflist}}

* {{cite bookcitation|authorauthor1-link = [[Michael R. Garey]]|first1=Michael and [[R.|last1=Garey|author2-link=David S. Johnson]]|first2=David S.|last2=Johnson | year = 1979 | title = [[Computers and Intractability: A Guide to the Theory of NP-Completeness]] | publisher = W.H. Freeman | isbn = 978-0-7167-1045-5}}|postscript=. A2.1: ND1, pgp.&nbsp;206.|title-link=Computers and Intractability: A Guide to the Theory of NP-Completeness}}

*{{cite articlecitation| authorfirst1=[[Martin |last1=Fürer]] and [[|first2=Balaji |last2=Raghavachari]]|year=1994|title=[[ Approximating the Minimumminimum-Degreedegree Steiner Treetree to within Oneone of Optimal]]optimal|journal= Journal of Algorithms }} |volume=17(|issue=3):409-423|pages=409–423|doi=10.1006/jagm.1994.1042|postscript=.|citeseerx=10.1.1.136.1089}}

*{{cite article| author=[[Martin Fürer]] and [[Balaji Raghavachari]]|year=1994|title=[[ Approximating the Minimum-Degree Steiner Tree to within One of Optimal]]|journal= Journal of Algorithms }} 17(3):409-423.

[[Category:Spanning tree]]

[[Category:NP-complete problems]]

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